The motion of a vehicle through the atmosphere at high supersonic speeds (particularly at Mach numbers greater than 1.4) produces shockwaves from the vehicle fore-body, lifting surfaces, propulsion systems, tail structures and other elements. These shockwaves coalesce far below the vehicle and before they reach the ground and form overpressure regions associated with the phenomenon referred to as a sonic boom. These shockwaves and sonic booms create noise conditions on the ground that are unacceptable to the general public and prohibited by FAA regulations. As a result, it has proven to be impractical to create large commercial supersonic transports, such as that envisioned by the NASA High Speed Civil Transport (HSCT) program that can operate over inhabited areas. For instance, the European Concorde, which operated at supersonic speeds, was limited to only over water operation, and was restricted to only selected airports while it was in service because of the noise associated with its flight. Such limitations make it financially impractical to create the next generation of supersonic transports.
Sonic booms are created by supersonic vehicles as they push the oncoming air out of their path. It is a natural effect of supersonic flight. Previous methods of controlling sonic booms have been proposed, but none have offered sufficient promise to enable vehicle development to proceed. For example, vehicle concepts have been proposed in which their shape and lift distribution have been modified along with reducing the vehicle weight to partially limit the ground noise created from supersonic flight. Other methods have been proposed that incorporate structures (such as rings) around the fuselage to reflect the shockwaves from sections of the vehicle thereby preventing the shockwaves from propagating to the ground. These structural changes significantly increase the length of the vehicles, produce inefficient volumes for passengers and cargo, and alter their lift and flight stability and control systems in ways that so far have proven to be incompatible with cost effective design and operation of the vehicles. Other concepts have been proposed which use energy methods involving plasma processes on the surface or very near the vehicle. These concepts are ineffective because they do not impact the far field noise generating processes of the sonic boom.